How many bolts or nuts are holding each wheel of your car? That number is probably 4 or 5, but why not just 1? Some sports cars have wheels with center lugs. Obviously that’s fewer parts, so why not all cars are like this?
For racing cars, this is an obvious choice, because wheels are changed often during the race and pit stops need to be quick. You have definitely seen this in Formula 1 – during a 2-3 second pit stop all 4 wheels are changed and centerlock wheelnuts are absolutely essential for that operation.
Central wheel lugnuts became common at the beginning of the 20th century. The British company Rudge-Whitworth came up with this way of securing wire rims to the car. The Rudge-Whitworth system was considered fast, because previously there was simply no standard solution for fixing the wheels to the car. But over time, the multi-bolt or nut systems became more popular. Take a look at the Ferrari Testarossa – early examples of this iconic supercar from 1984-1996 used centrerlock wheels:
And the later Testarossas have 5 bolt-on wheels. And it has nothing to do with power if that’s what you’re thinking. So, what are the advantages and disadvantages of centerlock wheels?
Advantages of centerlock wheels
Speed – 1 nut can be done-undone faster than 4 or 5. This is especially important in motorsports.
Sporty appearance – being linked to motorsports has a special image.
Weight and balance – Single center lugnut often weighs a little less than 4 or 5 fasteners. Also, that weight is very close to the axis of rotation of the wheel, making the wheel easier to balance.
Space – A rim with single center nut will have less contact area with the hub, allowing more space for brake cooling.
Strength – Strangely enough, a large single nut in the very center of the rim can hold the wheel on tighter. Also, because of the thread, that lugnut only tightens as the car is driving.
One big disadvantage of centerlock wheels
Force needed to tighten/loosen the nut – the old Rudge-Whitworth nuts mentioned above were literally hammered loose. These nuts had special wings on them to be struck with a copper or lead hammer. In the late 1960s, authorities in the U.S. and Germany banned such winged wheel nuts and manufacturers replaced hammers with huge spanners with very long handles to provide enough leverage to actually undo those lugnuts.
Early Testarossa buyers complained that they were afraid to take their supercars on long continent-crossing trips because they might be stranded by the side of the road if they cannot undo those nuts. That single wheelnut of the early Testarossa needs to be tightened with a torque of 440 Nm and undoing it somewhere in the middle of rural France or Italy might be a challenge.
In addition, 4-5 fasteners provide some insurance against the human error. If 1 out of 5 bolts or nuts are damaged or lost, nothing terrible should happen. And if the only single nut is damaged, your trip is over.
Finally, the multi-bolt or multi-nut solution is cheaper because it uses more popular, simpler parts. No extra unique tools required.
